Coccus, B.P. Cochineal. Carminum.

COCCUS, B.P.COCHINEAL.

Cochineal consists of the dried fecundated female insect, Coccus Cacti, Linn. (Order Hemiptera), reared on Nopalea coccinellifera, Salm-Dyck (N.O. Cactaceae), and other species of Nopalea. It is also official in the U.S.P. The insects are indigenous to Central America and Mexico, but the drug is now chiefly obtained from the Canary Islands. After fecundation, the insects develop an abundance of red colouring matter. They are then collected by brushing them off the plants, and killed by the fumes of burning charcoal or sulphur, or by stove heat or hot water, "silver-grain" cochineal resulting in the former case, whilst "black- grain" cochineal is obtained when heat is applied. The dried insects are about 5 millimetres long, oval in outline, flat or slightly concave on one side, and arched on the other. They are wrinkled transversely, nearly black ("black-grain") or greyish ("silver-grain") in colour, and brittle, readily yielding a dull, purplish powder. When macerated with water no insoluble powder should separate. Incinerated with free access of air, the drug should not yield more than 10 per cent. of ash (B.P. and U.S.P., 6 per cent). Cochineal is often artificially weighted with inorganic matter. In the case of the silver-grain variety, barium or lead carbonate or sulphate is used, while the black-grain variety in "faced" with black lead, ivory black, or manganese dioxide, or may contain very dark grains of magnetic sand containing iron. These adulterants are readily detected by soaking the drug in water, or by the abnormally high ash.

Constituents.—The chief constituent of cochineal is about 10 per cent. of carminic acid, obtainable in small red prismatic crystals, soluble in water, alcohol, and alkaline solutions. About 10 per cent. of fat and 2 per cent. of wax are also present, as well as albuminoids and inorganic matter. The fat consists almost entirely of free oleic, linoleic, and myristic acids.

Uses.—Cochineal is used principally as a colouring agent. A tincture of cochineal is prepared and sometimes used as an ingredient of cough mixtures, but it has no medicinal virtues. The brilliant red colouring matter of the cochineal insect is best seen as carmine and its preparations. Tincture of cochineal tends to form a cloudy mixture with water, owing to the presence of some fat, and solution of carmine gives a brighter tint. Preparations of cochineal are turned yellow by the mineral acids and become purple with alkalies. The colouring matter is often precipitated by the salts contained in hard tap-water, and distilled water only should be used for dilution.

Used to colour mixtures, lotions, mouth washes, etc., and it is also employed in culinary operations. It imparts a rose-pink or crimson colour to neutral or alkaline liquids, and a scarlet colour to acid liquids. This solution mixes more readily, and imparts a more brilliant colour, than ordinary solutions of cochineal. If desired the alcohol may be replaced by glycerin (see Glycerinum Cocci).

Tinctura Cocci, B.P.—TINCTURE OF COCHINEAL.

Cochineal, in powder, 10; alcohol (4.5 per cent.), 100. Prepared by the maceration process. Tincture of cochineal is used chiefly as a colouring agent, and as an indicator in alkalimetry. It is rendered more miscible by the addition of about 10 per cent. of potassium citrate. Dose.—3 to 10 decimils (0.3 to 1.0 milliliters) (5 to 15 minims).

CARMINUM.CARMINE.

Carmine is a brilliant red colouring matter prepared from cochineal, either by precipitating an aqueous infusion with alum, or by extracting with dilute sodium carbonate solution and adding white of egg and sulphuric acid. It occurs in light, bright red pieces, which can readily be reduced to powder. Carmine contains about 50 per cent. of carminic acid, and should not leave more than 9 per cent. of ash, consisting chiefly of calcium and aluminium oxides. Carmine gives on heating an odour of burnt feathers. It should dissolve readily in dilute solution of ammonia, leaving only a slight residue of aluminium hydroxide. It may be compared with a pure standard specimen by rubbing 1 decigram of each with 10 grammes of starch and noting the depth of colour produced. Carmine should not be exposed to light. It is sometimes adulterated with inorganic matter (e.g., aluminium oxide or barium sulphate), or with aniline dyes.

Insoluble in water or diluted acids.

Uses.—Carmine is used to colour ointments, tooth powders, tooth washes, dusting powders, and other pharmaceutical preparations. If used in solid form prolonged trituration with powder is necessary to obtain a good colour and even distribution. To obtain the maximum of colour the carmine should be dissolved in a small quantity of strong solution of ammonia and triturated with the powder. A good solution for colouring neutral or alkaline mouth washes and mixtures is Liquor Carmini, an ammoniacal aqueous solution, of which 3 or 4 drops to the fluid ounce of liquid is sufficient. The colouring matter of Liquor Carmini is precipitated in acid solutions. Carmine is much used for staining histological specimens; it is less fugitive than the aniline colours.

PREPARATIONS.

Glycerinum Carmini, B.P.C.—GLYCERIN OF CARMINE. 1 in 16.

Glycerin of carmine is but slightly alkaline, and has a pure carmine tint. It is a suitable colouring agent for neutral or alkaline liquids, 3 decimils (0.3 milliliters) (5 minims) being added to 30 mils (1 fluid ounce) of mixture. For many purposes, however, Glycerinum Cocci will be found more suitable.

Solution of carmine is a suitable colouring agent for alkaline mixtures, month washes, lotions, etc., in the proportion of about 1 per cent. The red colouring matter is precipitated by acids; for colouring acid mixtures tincture of cudbear should be employed. The "Liquor Rosae Dulcis'' of commerce is usually prepared from carmine.